The Mechanics of Rocking Stones: Equilibria on Separated Scales |
| |
Authors: | Gábor Domokos András árpád Sipos Tímea Szabó |
| |
Institution: | 1. Department of Mechanics, Materials and Structures, Budapest University of Technology and Economics, M??egyetem rkp. 3., K242, 1111, Budapest, Hungary
|
| |
Abstract: | Rocking stones, balanced in counter-intuitive positions, have always intrigued geologists. In our paper, we explain this phenomenon
based on high-precision scans of pebbles which exhibit similar behavior. We construct their convex hull and the heteroclinic
graph carrying their equilibrium points. By systematic simplification of the arising Morse–Smale complex in a one-parameter
process, we demonstrate that equilibria occur typically in highly localized groups (flocks), the number of the latter being
reliably observed and determined by hand experiments. Both local and global (micro and macro) equilibria can be either stable
or unstable. Most commonly, rocks and pebbles are balanced on stable local equilibria belonging to stable flocks. However,
it is possible to balance a convex body on a stable local equilibrium belonging to an unstable flock and this is the intriguing
mechanical scenario corresponding to rocking stones. Since outside observers can only reliably perceive flocks, the last described
situation will appear counter-intuitive. A comparison between computer experiments and hand experiments reveals that the latter
are consistent, that is, the flocks can be reliably counted and the pebble classification system proposed in our previous
work is robustly applicable. We also find an interesting logarithmic relationship between the flatness of pebbles and the
average number of global equilibrium points, indicating a close relationship between classical shape categories and the new
classification system. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|